William D. Hamilton Remembered  A
revolutionary thinker, Hamilton gave biologists the tools for understanding
sociality in all organisms.

by Richard D. Alexander

William D. Hamilton

William D. Hamilton died of malaria in England on
March 7 at the age of 63. Although he had pondered the evolutionary
impact of diseases for much of his professional life, he died because
he had traveled to damp equatorial Africa unfortified by
malaria-fighting drugs. Some may see this as indicating a paucity of
common sense. Bills forte was, indeed, not common sense but an
astonishing fund of uncommon sense. Perhaps if he'd had much more
common sense, he might not have provided the rest of us with the
insights that have caused him to be described as the greatest
evolutionary biologist of his generation.

Bill's
extensive field meanderings, especially in the New World and Old World
tropics, and his breadth of curiosity, about natural history appear to
have beenfor him as for Darwina source of ideas richer than
most of us can imagine. He ranged similarly across the literature of
biology, seeing it, too, as a flood of significant anecdotes. Except
for his own amazing internal logic and the "maths" with which he backed
it up, he relied on others to test his theories and was delighted when
any such effort succeeded.

Bill's originality of mind often turned the barely
articulated ideas of distinguished predecessorsideas overlooked
or neglected by all the rest of usinto magnificent theoretical
edifices affecting our view of all life. He expanded Charles Darwin's
explanation of the existence of sterile castes it insects and combined
it with Ronald Fisher's hint about quantifying altruism in caterpillars
toward siblings, creating a comprehensive theory accounting for
underlying patterns of sociality in all organisms. Similarly, Hamilton
converted a maddeningly cryptic question about territory and sex ratios
(the proportions of males and females in populations), posed by Fisher
in 1930, into a broadly enlightening explanation of why the females of
thousands of insect species have so many daughters and so few sons.
Such females mate with a brother (who provides no parental care) and
determine the sex of each egg as it is laid (a determination made
possible because males derive from unfertilized eggs). Bill argued that
for such females to make more or hardier males than are sufficient
merely to fertilize the eggs would be an unnecessary cost. His logic on
these and other seemingly parochial topics affected the way biologists
approached far broader issues, such as our views of the levels at which
natural selection has operatedfrom genes to individuals and
species, as well as from families to tribes and nationsand thus
the basic reasons for organisms acting as they do.

Bill also contributed extensively to the development
of many other theories, such as George Williams's now widely accepted
pleiotropic theory of senescence (the idea that because selection is
less powerful later in life, incidental deleterious effects late in
life can persist if they are accidental consequences of reproductively
beneficial effects of the same genes early in life); the so-called Red
Queen hypothesis, including the idea that the costly process of sexual
(as opposed to asexual) reproduction pays for itself by enabling
organisms to outrace rapidly multiplying pathogens and parasites; and
Robert Trivers's theory of reciprocal altruism among
even unrelated individuals. One of my favorite Hamilton essays is
"Geometry for the Selfish Herd," in which he explains how even the
seemingly random strollings and mergings of individuals, as in a
foraging bird flock or mammal herd, are almost certainly strategies
that involve continual trade-offs between such alternatives as obtaining
the best food and placing other individuals between the strategist and
possible predators.

I once heard Bill assert that he avoided applying
his theories to humans because he thought such extrapolation was too
difficult and too subject to misinterpretation (a reluctance he later
overcame). Yet only his theory of nepotism accounts for the universal
human ability to respond to differing degrees of relatedness among
relatives and for the varied patterning of human kinship systems in
hundreds of societies in different situations worldwide. Extensive
differential nepotism (meaning assistance to a wide variety of
relatives, meted out so as to take into account the degree of genetic
relatedness to oneself) is the crowning glory of Hamilton's theory,
yet it is still known only in humans.

It is curious that Bill, who received an
unprecedented array of international honors, was never made a foreign
associate of the U.S. National Academy of Sciences and that one still
hears even some prominent biologists dismissing his work. I see this
startling attitudewhich all evolutionary biologists are now and
then required to endureas a reflection of the difficulty that
even thoughtful and educated people often have in fairly evaluating
findings in the field of evolutionary history that purport to account
for day-to-day human behavior. Bill Hamilton, as much as or more than
any other twentieth-century biologist, provided the basic tools for
understanding and modifying such resistance. It is now up to the rest
of us to use and develop all such glimpses into the human condition to
generate a self-understanding adequate to the task of significantly
reducing human misery and strife across the globe.

Richard D. Alexander is T. H. Hubbell Distinguished University
Professor of Evolutionary Biology and Curator of Insects at the
University of Michigan's Museum of Zoology.